Backlight unit

ABSTRACT

A back light unit includes a light source and a light guide unit having a first surface emitting light to a display panel, a second surface facing the first surface, and a plurality of connecting surfaces connecting the first surface and the second surface. The connecting surfaces includes a first side surface, a second side surfaces and a third side surface between the first side surface and a second side surface, A first included angle of the first incident surface and the first diffusion surface is equal to or greater than about 90 degree.

CROSS-REFERENCE TO RELATED APPLICATION

This U.S. non-provisional patent application claims priority under 35U.S.C. §119 of Korean Patent Application No. 10-2013-0003070, filed onJan. 10, 2013, the contents of which are hereby incorporated byreference in its entirety.

BACKGROUND

1. Field of Disclosure

Embodiments of the present disclosure relate to a backlight unit. Moreparticularly, embodiments of the present disclosure relate to abacklight unit capable of reducing a light leakage.

2. Description of the Related Art

In general, a display device is classified into a transmissive typedisplay device, a transflective type display device, and a reflectivetype display device. Among them, each of the transmissive type displaydevice and the transflective type display device includes a displaypanel to display an image and a backlight unit to supply light to thedisplay panel.

The backlight unit includes a light source to generate the light and alight guide unit to guide the light from the light source to the displaypanel.

A point light source may be used as the light source. The point lightsource includes a light emitting device, e.g., a light emitting diode.The light source is disposed to correspond to at least one incidentsurface of the light guide unit.

A portion of the light incident into the light guide unit through theincident surface is lost. Thus, efficiency of the backlight unit may bedeteriorated.

SUMMARY

The present disclosure provides a backlight unit having high lightefficiency.

Embodiments of the inventive concept provide a backlight unit includinga light source each emitting light, and a light guide unit that includesa first surface emitting light to a display panel, a second surfacefacing the first surface, and a plurality of connecting surfacesconnecting the first surface and the second surface, the light guideunit guide the light from the light source to the display panel, theconnecting surfaces comprising a first side surface extending in a firstdirection, a second side surface facing the first side surface, a thirdside surface extending in a second direction substantially perpendicularto the first direction; and a first incident surface disposed betweenthe first side surface and the third side surface, the first incidentsurface receiving the light from the light source and including at leastone first serration pattern having a first diffusion surface and asecond diffusion, the second diffusion surface being closer to the thirdside surface than the first diffusion surface.

A first included angle of the first incident surface and the firstdiffusion surface may be equal to or greater than about 90. The firstincluded angle may be equal to or smaller than 120 degree.

The first included angle of the first incident angle and the firstdiffusion surface may be equal to or smaller than 117 degree.

The at least one first serration pattern may be provide in a pluralnumber and a second included angle of the first incident surface and thesecond diffusion surface of one of the first serration patterns may bediffer from a second included angle of the first incident surface andthe second diffusion surface of other one of the first serrationpatterns.

Each of the first serration patterns may further include a thirddiffusion surface disposed between the first diffusion surface and thesecond diffusion surface and the third diffusion surface may besubstantially parallel to the first incident surface.

The first serration patterns may be spaced apart each other.

The second included angle surface may be equal to or greater than about35 degree and equal to or smaller than 60 degree.

The at least one first serration pattern may include two serrationpatterns, the at least one first serration pattern further includes aportion of the first incident surface disposed between two firstserration patterns.

Embodiments of the inventive concept provide a backlight unit includinga light source emitting a light, and a light guide unit that includes afirst surface, a second surface facing the first surface, and aplurality of connecting surfaces connecting the first surface and thesecond surface to guide the light from the light source. The connectingsurfaces may include a first side surface extending in a firstdirection, a second side surface facing the first side surface, a thirdside surface that extends in a second direction crossing the firstdirection, a first incident surface disposed between the first sidesurface and the third side surface, receiving the light from the lightsource, and including at least one first serration pattern having afirst diffusion surface and a second diffusion surface. The firstincident surface may define a first included angle with respect to anextension surface of the third side surface. A second included angle ofthe first diffusion surface with respect to the first incident surfacemay be in a range determined by the following Equation, and a thirdincluded angle of the second diffusion surface with respect to the firstincident surface may be smaller than the second included angle,

Equation

90≦θ2≦90+θ1, where θ2 denotes the second included angle and θ1 denotesthe first included angle. The first included angle may be greater thanabout 20 degrees and smaller than about 30 degrees.

The back light unit may further include a second incident surfacedisposed between the second side surface and the third side surface,receiving the light from the light source, and including at least onesecond serration pattern,

The first incident surface may have a shape symmetrical with a shape ofthe second incident surface when viewed in a plan view.

The first serration pattern may further comprise a third diffusionsurface disposed between the first diffusion surface and the seconddiffusion surface.

The first serration pattern may be provided in a plural number.

Any one of the first serration patterns may have a shape different froma shape of another one of the first serration patterns when viewed in aplan view.

An included angle between the third side surface and the seconddiffusion surface of each of the any one of the first serration patternsand the another one of the first serration patterns may be equal to orgreater than about 35 degrees and equal to or smaller than about 60degrees.

The display panel receives the light from the light guide unit. Theeffective light emitting area of the light guide unit corresponds to thedisplay area of the display panel. The light guide unit provides theuniform light to the display area. The light guide unit having theimproved light efficiency provides the light with high brightness to thedisplay panel. Therefore, the display device may improve the displayquality of the image displayed thereon.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other advantages of the present disclosure will becomereadily apparent by reference to the following detailed description whenconsidered in conjunction with the accompanying drawings wherein:

FIG. 1 is a perspective view showing a backlight unit according to anexemplary embodiment of the present disclosure;

FIG. 2 is a plan view showing a backlight unit shown in FIG. 1;

FIG. 3 is a plan view showing an effective light emitting area of alight guide unit according to a first included angle;

FIGS. 4A and 4B are plan views showing a first light incident area and asecond light incident area shown in FIG. 2, respectively;

FIGS. 5A and 5B are perspective views respectively showing the first andthe second light incident areas shown in FIGS. 4A and 4B;

FIG. 6 is a plan view showing a first light incident area according toan exemplary embodiment of the present disclosure;

FIG. 7 is a plan view showing a first light incident area according toan exemplary embodiment of the present disclosure;

FIGS. 8A and 8B are views showing a distribution of light according to aserration pattern;

FIGS. 9 to 13 are plan views showing first light incident areasaccording to exemplary embodiments of the present disclosure;

FIGS. 14A to 14F are plan views showing light guide units according toexemplary embodiments of the present disclosure; and

FIG. 15 is an exploded perspective view showing a display deviceaccording to an exemplary embodiment of the present disclosure.

DETAILED DESCRIPTION

It will be understood that when an element or layer is referred to asbeing “on”, “connected to” or “coupled to” another element or layer, itcan be directly on, connected or coupled to the other element or layeror intervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on,” “directly connected to”or “directly coupled to” another element or layer, there are nointervening elements or layers present. Like numbers refer to likeelements throughout. As used herein, the term “and/or” includes any andall combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer or section fromanother region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of the present invention.

Spatially relative terms, such as “beneath”, “below”, “lower”, “above”,“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms, “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “includes”and/or “including”, when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

Hereinafter, the present invention will be explained in detail withreference to the accompanying drawings.

FIG. 1 is a perspective view showing a backlight unit according to anexemplary embodiment of the present disclosure, FIG. 2 is a plan viewshowing a backlight unit shown in FIG. 1, and FIG. 3 is a plan viewshowing an effective light emitting area of a light guide unit accordingto a first included angle.

Referring to FIGS. 1 and 2, the backlight unit includes a light sourcethat emits light and a light guide unit LG that receives the light fromthe light source and guides the light.

The backlight unit includes a first light source LE1 and a second lightsource LE2. The first light source LE1 and the second light source LE2provide the light to different areas of the light guide unit LG. Each ofthe first and the second light sources LE1 and LE2 includes two lightemitting devices. The number of the light emitting devices should not belimited to two in each of the first and the second light sources LE1 andLE2. In addition, the light emitting device may be, but not limited to,a light emitting diode.

The light guide unit LG includes a first surface US, a second surfaceLS, and a plurality of connecting surfaces IS1, IS2, and CS1 to CS4 thatconnect the first surface US and the second surface LS.

As shown in FIGS. 1 and 2, the light guide unit LG has a rectangularplate shape in which two corner portions thereof are cut away, but theshape of the light guide unit LG should not be limited to therectangular plate shape. The two cut-away corner portions will bereferred to as a first light incident area AA and a second lightincident area BB, respectively. The first light incident area AA and thesecond light incident area BB respectively receive the lights from thefirst light source LE1 and the second light source LE2. The number ofthe cut-away corner portions should not be limited to two. The number ofthe cut-away corner portions may be four formed at all the four cornersof the rectangular plate. The number of the cut-away corner portions maybe one formed at one corner of the rectangular plate. That is, one ofthe first light incident area AA and the second light incident area BBmay be omitted.

The light incident into the first light incident area AA and the secondlight incident area BB exits from the first surface US, and thushereinafter the first surface US is referred to as a light exit surface.The second surface LS faces the light exit surface US in a thicknessdirection of the light guide unit LG. Hereinafter, the second surface LSis referred to as an opposite surface.

The connecting surfaces IS1, IS2, and CS1 to CS4 include a firstincident surface IS1, a second incident surface IS2, and at least threeside surfaces. FIGS. 1 and 2 show the light guide unit LG having first,the second, the third, and the fourth side surfaces CS1, CS2, CS3, andCS4.

The first and the second side surfaces CS1 and CS2 extend in a firstdirection D1. The first and the second side surfaces CS1 and CS2 arespaced apart from each other and face each other. The third side surfaceCS3 extends in a second direction D2 crossing the first direction D1.The fourth side surface CS4 faces the third side surface CS3 andconnects the first side surface CS1 and the second side surface CS2. Thesecond direction D2 may be substantially perpendicular to the firstdirection D1. Hereinafter, the following description will be describedunder the condition that the first direction D1 and the second directionD2 are perpendicular to each other.

The first incident surface IS1 and the second incident surface IS2 arerespectively disposed in the first light incident area AA and the secondlight incident area BB. The first incident surface IS1 faces the firstlight source LE1 and the second incident surface IS2 faces the secondlight source LE2.

The first light source LE1 includes a first light emitting surface ES1facing the first incident surface IS1 and the second light source LE2includes a second light emitting surface ES2 facing the second incidentsurface IS2. The light which is generated in the first light source LE1and the second light source LE2 comes out through the first lightemitting surface ES1 and the second light emitting surface ES2.

As shown in FIG. 2, the first light emitting surface ES1 and the secondlight emitting surface ES2 is parallel to the first incident surface IS1and the second incident surface IS2, respectively. In other embodimentof the present disclosure, at least one of the first light emittingsurface ES1 and the second light emitting surface ES2 may be notparallel to corresponding light emitting surface. In detail, the firstincident surface IS1 is disposed between the first side surface CS1 andthe third side surface CS3. The first incident surface IS1 connects thefirst side surface CS1 and the third side surface CS3. The secondincident surface IS2 is disposed between the second side surface CS2 andthe third side surface CS3. The second incident surface IS2 connects thesecond side surface CS2 and the third side surface CS3.

However, the connections of the connecting surfaces IS1, IS2, and CS1 toCS4 should not be limited to the above-mentioned connections. That is,additional surfaces may be disposed between the first incident surfaceIS1 and the first side surface CS1 or between the first incident surfaceIS1 and the third side surface CS3, and additional surfaces may bedisposed between the second incident surface IS2 and the second sidesurface CS2 or between the second incident surface IS2 and the thirdside surface CS3.

Referring to FIG. 2, the light guide unit LG includes an effective lightemitting area LA and a peripheral area NLA. Here, the effective lightemitting area LA corresponds to a display area of a display panel (notshown). In other words, the effective light emitting area LA is aminimum area required to generate an effective image in the displaypanel.

When the effective light emitting area LA of the light guide unit LG issmaller than the display area of the display panel, a display quality ofthe effective image is degraded. The brightness of the effective imagedepends on positions in the display area. For instance, the imagedisplayed on the edge portion of the display area has brightness lowerthan brightness of the image displayed in a center portion of thedisplay area.

The peripheral area NLA corresponds to and overlaps with a non-displayarea of the display panel (not shown). The image is not displayed in thenon-display area. The effective light emitting area LA is surrounded bythe peripheral area NLA.

The effective light emitting area LA of the light guide unit LG isvaried depending on the arrangement of the first incident surface IS1and the second incident surface IS2. The first and the second incidentsurfaces IS1 and IS2 are inclined with respect to the third side surfaceCS3. As shown in FIG. 2, each of the first and the second incidentsurfaces IS1 and IS2 is inclined with respect to an extension surfaceCS30 of the third side surface CS3 at a first included angle θ1.

The first included angle θ1 is greater than about 20 degrees and smallerthan about 30 degrees. When the first included angle θ1 is equal to orsmaller than about 20 degrees, the brightness of the effective lightemitting area LA in the center portion and in the edge portion becomesnon-uniform. This is because the light incident to the first and thesecond incident surfaces IS1 and IS2 has angles with respect to thefirst side surface CS1 and the second side surface CS2, respectively.

When the first included angle θ1 is equal to or greater than about 30degrees, the light guide unit LG has a relatively smaller effectivelight emitting area LA. FIG. 3 shows a first light guide unit LG₂₇having the first included angle θ1 of about 27 degrees and a secondlight guide unit LG₄₅ having the first included angle θ1 of about 45degrees with respect to the third side surface. The area of theeffective light emitting area LA₄₅ of the second light guide unit LG₄₅is smaller than the area of the effective light emitting area LA₂₇ ofthe first light guide unit LG₂₇. The second light guide unit LG₄₅provides the light with a relatively non-uniform brightness to thedisplay area as compared to the first light guide unit LG₂₇.

Therefore, the first included angle θ1 is required to be in a range fromabout 20 degrees to about 30 degrees, preferably in a range greater thanabout 24 degrees and smaller than about 27 degrees, in order to providethe light with the uniform brightness throughout the effective lightemitting area LA.

Meanwhile, according to another embodiment, the included angle betweenthe first incident surface IS1 and the extension surface CS30 of thethird side surface CS3 may be different from the included angle betweenthe second incident surface IS2 and the extension surface CS30 of thethird side surface CS3.

FIGS. 4A and 4B are plan views showing the first light incident area andthe second light incident area shown in FIG. 2, respectively, and FIGS.5A and 5B are perspective views respectively showing the first and thesecond light incident areas shown in FIGS. 4A and 4B.

At least one first serration pattern NP1 is formed in the first incidentsurface IS1, and at least one second serration pattern NP2 is formed inthe second incident surface IS2. The at least one first serrationpattern NP1 is disposed in the first light incident area AA (refer toFIG. 2), the at least one second serration pattern NP2 is disposed inthe second light incident area BB (refer to FIG. 2).

The first serration pattern NP1 includes grooves formed in the firstincident surface IS1 and the second serration pattern NP2 includesgrooves formed in the second incident surface IS2. The first serrationpattern NP1 and the second serration pattern NP2 may have a sawtooth.

Hereinafter, the first serration patterns NP1 and the second serrationpatterns NP2 will be described in detail. FIGS. 4A, 4B, 5A, and 5B showthe first incident surface IS1 in which first serration patterns NP1 arearranged and the second incident surface IS2 in which second serrationpatterns NP2 are arranged. The first serration patterns NP1 may includesix first serration patterns NP1-1 to NP1-6 and the second serrationpatterns NP2 may include six second serration patterns NP2-1 to NP2-6.The number of each of the first serration patterns NP1 and the secondserration patterns NP2 should not be limited to six.

Referring to FIGS. 4A, 4B, 5A, and 5B, the first and second incidentsurfaces IS1 and IS2 are symmetrical with each other when viewed on thelight exit surface US. Hereinafter, the first incident surface IS1 willbe described in detail. Meanwhile, the second incident surface IS2 mayhave the same shape as the first incident surface IS1, but it should notbe limited thereto or thereby.

As shown in FIGS. 4A and 5A, each of the first serration patterns NP1-1to NP1-6 includes a first diffusion surface DS1 and a second diffusionsurface DS2. The first diffusion surface is closer to the first sidesurface or the second side surface than the second diffusion surface.Each of the first serration patterns NP1-1 to NP1-6 is a triangularprism shape.

The first diffusion surface DS1 diffuses a portion of the light incidentto the first incident surface IS1 to allow the portion of the light totravel to the first side surface CS1. The second diffusion surface DS2diffuses the other portion of the light incident to the first incidentsurface IS1 to allow the other portion of the light to travel to thesecond side surface CS2 (refer to FIG. 2).

Referring to FIGS. 4A and 5A, the first serration patterns NP1-1 toNP1-6 have the same shape when viewed on the light exit surface US. Thefirst diffusion surface of any one of the first serration patterns NP1-1to NP1-6 is connected to the second diffusion surface of another one ofthe first serration patterns, which is adjacent to the any one of thefirst serration patterns NP1-1 to NP1-6. For instance, the firstdiffusion surface DS1 of the second first-serration pattern NP1-2 of thefirst serration patterns NP1-1 to NP1-6 is directly connected to thesecond diffusion surface DS2 of the first-serration pattern NP1-1adjacent to a right side of the second first-serration pattern NP1-2.

FIG. 6 is a plan view showing the first light incident area according toan exemplary embodiment of the present disclosure, FIG. 7 is a plan viewshowing the first light incident area according to an exemplaryembodiment of the present disclosure, and FIGS. 8A and 8B are viewsshowing a distribution of light according to a serration pattern.

Referring to FIGS. 6 and 7, the first diffusion surface DS1 forms asecond included angle θ2 with respect to the first incident surface IS1and the second diffusion surface DS2 forms a third included angle θ3with respect to the first incident surface IS1. The second includedangle θ2 is different from the third included angle θ3.

The maximum value of the second included angle θ2 is shown in FIG. 6. Inthis case, the first diffusion surface DS1 is substantially parallel tothe first side surface CS1. The maximum value of the second angle θ2 maybe a 90 degree plus the first angle θ1. The first diffusion surface DS1parallel to the first side surface CS1 prevents the light incident tothe first incident surface IS1 from being diffused to the first sidesurface CS1. When the maximum value of the second included angle θ2 isgreater than that shown in FIG. 6, a difference between the brightnessof the light exiting from the center portion of the effective lightemitting area LA (refer to FIG. 2) and the brightness of the lightexiting from the edge portion of the effective light emitting area LA(refer to FIG. 2) increases. This is because a difference between anamount of the light diffused to the first side surface CS1 and an amountof the light diffused to the center portion of the light guide unit LGis increased. That is, when the maximum value of the second includedangle θ2 is greater than that shown in FIG. 6, the light provided to thedisplay panel becomes non-uniform according to the areas of the displayarea of the display panel.

The minimum value of the second included angle θ2 is shown in FIG. 7. Inthis case, the first diffusion surface DS1 is substantially vertical tothe first incident surface IS1. The first diffusion surface DS1 verticalto the first incident surface IS1 diffuses the light incident to thefirst incident surface IS1 to the first side surface CS1. When theminimum value of the second included angle θ2 is smaller than that shownin FIG. 7, a portion of the light diffused to the first side surface CS1is leaked through the first side surface CS1, and the amount of thelight leaked through the first side surface CS1 is greater than acritical amount of the light leakage for maintaining appropriateuniformity of light intensity throughout the display. That is, when theminimum value of the second included angle θ2 is smaller than that shownin FIG. 7, the light efficiency of the light guide unit LG is reduced.

The range of the second included angle θ2 is determined by the followingEquation.

Equation

90 degree≦second included angle (θ2)≦90 degree+first included angle(θ1), where the first included angle (θ1) is equal to or greater than 20degree and equal to or less than 30 degree. Preferably, the firstincluded angle (θ1) is equal to or greater than 24 degree and equal toor less than 27 degree.

When the second included angle θ2 satisfies the range determined by theEquation, the third included angle θ3 has an acute angle smaller thanthe second included angle θ2.

FIGS. 8A and 8B show a traveling path of the light incident through thesecond incident surface IS2. FIG. 8A shows the traveling path of thelight incident to the second serration patterns having the same secondand third included angles θ2 and θ3, which are the same acute angle, andFIG. 8B shows the traveling path of the light incident to the lightguide unit according to the present exemplary embodiment. The lightguide unit having the traveling path of the light shown in FIG. 8Bincludes the second serration patterns having the second included angleθ2 determined by the Equation and the third included angle θ3 smallerthan the second included angle θ2.

The amount of the light leaked through the second side surface CS2 ofthe light guide unit having the traveling path shown in FIG. 8A isgreater than that of the light leaked through the second side surfaceCS2 of the light guide unit having the traveling path shown in FIG. 8B.Thus, the light efficiency of the light guide unit shown in FIG. 8A islower than the light efficiency of the light guide unit shown in FIG.8B. The light guide unit having the traveling path shown in FIG. 8B mayprovide the light to the display panel, which is enough to generate theeffective image.

FIGS. 9 to 13 are plan views showing first light incident areasaccording to another exemplary embodiment of the present disclosure. InFIGS. 9 to 13, detailed descriptions of the same elements as those shownin FIGS. 1 to 8B are omitted.

Referring to FIGS. 9 and 11, each of first serration patterns NP1-1 toNP1-6 includes a first diffusion surface DS1 and a second diffusionsurface DS2. The first serration patterns NP1-1 to NP1-6 have the sameshape when viewed on the light exit surface US.

The first serration patterns NP1-1 to NP1-6 of a light guide unit LG30shown in FIG. 9 are spaced apart from each other at regular intervals. Aportion of the first incident surface IS1 is disposed between two firstserration patterns adjacent to each other among the first serrationpatterns NP1-1 to NP1-6.

The first diffusion surface of any one of the first serration patternsNP1-1 to NP1-6 of a the light guide unit LG40 shown in FIG. 10 isconnected to the second diffusion surface of another one of the firstserration patterns NP1-1 to NP1-6, which is adjacent to the any one ofthe first serration patterns NP1-1 to NP1-6. For instance, the firstdiffusion surface DS1 of the second first-serration pattern NP1-2 of thefirst serration patterns NP1-1 to NP1-6 is directly connected to thesecond diffusion surface DS2 of the first-serration pattern NP1-1adjacent to a right side of the second first-serration pattern NP1-2.

In addition, the first diffusion surface DS1 of the first-serrationpattern of the first serration patterns NP1-1 to NP1-6 is directlyconnected to the first side surface CS1 and the second diffusion surfaceDS2 of the last first-serration pattern of the first serration patternsNP1-1 to NP1-6 is directly connected to the third side surface CS3. Forexample, the first diffusion surface DS1 of the first-serration patternof the first serration patterns NP1-1 to NP1-6 is directly connected tothe first side surface CS1 and the second diffusion surface DS2 of thesixth first-serration pattern of the first serration patterns NP1-1 toNP1-6 is directly connected to the third side surface CS3.

Each of the first serration patterns NP1-1 to NP1-6 of a light guideunit LG50 shown in FIG. 11 further includes a third diffusion surfaceDS3 disposed between the first diffusion surface DS1 and the seconddiffusion surface DS2. The third diffusion surface DS3 is substantiallyin parallel to the first incident surface IS1. The first serrationpatterns NP1-1 to NP1-6 of a light guide unit LG50 shown in FIG. 11 mayfurther includes the portion of the first incident surface IS1 disposedbetween two first serration patterns adjacent to each other among thefirst serration patterns NP1-1 to NP1-6.

However, the shape of the third diffusion surface DS3 should not belimited thereto or thereby. For instance, the third diffusion surfaceDS3 forms a predetermined angle with respect to the first incidentsurface IS1. In addition, the third surface DS3 has a two-dimensionalcurved shape when viewed on the light exit surface US.

Meanwhile, different from the first serration patterns shown in FIG. 11,only a portion of the first serration patterns NP1-1 to NP1-6 mayfurther include the third diffusion surface DS3 in the light guide unitaccording to another exemplary embodiment.

Referring to FIGS. 12 and 13, first serration patterns having differentshapes from each other are formed in the first incident surface IS1.FIG. 12 shows the first incident surface IS1 in which six firstserration patterns NP1-1 to NP1-6 are arranged and FIG. 13 shows thefirst incident surface IS1 in which four first serration patterns NP1-1NP1-4 are arranged.

The first serration patterns NP1-1 to NP1-6 of a light guide unit LG60shown in FIG. 12 have the same second included angle θ2 and differentthird included angles θ3 from each other. As shown in FIG. 12, the thirdincluded angle θ3 gradually increases from the first-serration patternsNP1-1 to the sixth first-serration pattern NP1-6 among the firstserration patterns NP1-1 to NP1-6. In this case, areas of the firstdiffusion surfaces DS1 of the first serration patterns NP1-1 to NP1-6are different from each other and the second diffusion surfaces DS2 ofthe first serration patterns NP1-1 to NP1-6 are different from eachother.

As shown in FIG. 12, the second diffusion surfaces DS2 of the firstserration patterns NP1-1 to NP1-6 are inclined with respect to the thirdside surface CS3. The second diffusion surfaces DS2 of the firstserration patterns NP1-1 to NP1-6 form different included angles withrespect to the extension surface CS30 of the third side surface CS3.

Among the first serration patterns NP1-1 to NP1-6, an included angleθ_(NP1-1) between the second diffusion surface DS2 of thefirst-serration pattern NP1-1 and the extension surface CS30 of thethird side surface CS3 has the minimum value among included anglesbetween the second diffusion surfaces DS2 and the extension surfaceCS30. In addition, an included angle θ_(NP1-6) between the seconddiffusion surface DS2 of the sixth first-serration pattern NP1-6 and theextension surface CS30 of the third side surface CS3 has the maximumvalue among the included angles between the second diffusion surfacesDS2 and the extension surface CS30.

The included angle θ_(NP1-1) between the second diffusion surface DS2 ofthe first-serration pattern NP1-1 and the extension surface CS30 of thethird side surface CS3 is greater than about 35 degrees. The includedangle θ_(NP1-6) between the sixth diffusion surface DS6 of the sixthfirst-serration pattern NP1-6 and the extension surface CS30 of thethird side surface CS3 is smaller than about 60 degrees.

The first serration patterns NP1-1 to NP1-4 of a light guide unit LG80shown in FIG. 13 have the same second included angle θ2 and differentthird included angles θ3 from each other. As shown in FIG. 13, the thirdincluded angle θ3 gradually decreases from the first-serration patternsNP1-1 to the fourth first-serration pattern NP1-4 among the firstserration patterns NP1-1 to NP1-4. In this case, areas of the firstdiffusion surfaces DS1 of the first serration patterns NP1-1 to NP1-4are the same and the second diffusion surfaces DS2 of the firstserration patterns NP1-1 to NP1-4 are different from each other.

Among the first serration patterns NP1-1 to NP1-4, an included angleθ_(NP1-1) between the second diffusion surface DS2 of thefirst-serration pattern NP1-1 and the extension surface CS30 of thethird side surface CS3 has the maximum value among included anglesbetween the second diffusion surfaces DS2 and the extension surfaceCS30. In addition, an included angle θ_(NP1-4) between the seconddiffusion surface DS2 of the fourth first-serration pattern NP1-4 andthe extension surface CS30 of the third side surface CS3 has the minimumvalue among the included angles between the second diffusion surfacesDS2 and the extension surface CS30.

Although not shown in figures, the second included angles θ2 of thefirst serration patterns NP1-1 to NP1-4 may be different from each otherin the range determined by the Equation.

FIGS. 14A to 14F are plan views showing light guide units according toexemplary embodiments of the present disclosure. In FIGS. 14A to 14F,detailed descriptions of the same elements as those shown in FIGS. 1 to13 will be omitted.

Referring to FIG. 14A, a third side surface CS3 of a light guide unitLG82 may be a circular arc surface. Accordingly, the extension surfaceCS30 (refer to FIG. 4) of the third side surface CS3 may be extendedfrom a surface CS300 connected between sides disposed at both ends ofthe third side surface CS3. Different from the third side surface CS3shown in FIG. 14A, the third side surface CS3 may be a concave circulararc surface.

Referring to FIG. 14B, a third side surface CS3 of a light guide plateLG82 includes a first circular arc surface CS3-1 and a second circulararc surface CS3-2. The first circular arc surface CS3-1 is connected tothe first incident surface IS1 and the second circular arc surface CS3-2is connected to the second incident surface IS2.

Referring to FIG. 14C, each of first and second side surfaces CS1 andCS2 of a light guide unit LG83 may be the circular arc surface.

Referring to FIG. 14D, a fourth side surface CS4 of a light guide unitLG84 may be a circular arc surface. According to embodiment, the first,second, and fourth side surfaces CS1, CS2, and CS4 may be a circular arcsurface.

Referring to FIG. 14E, a first light incident area AA and a second lightincident area BB of a light guide unit LG85 may be convex from the lightexit surface US when viewed in a plan view. Auxiliary surfaces CS1-10and CS3-10 are disposed between the first incident surface IS1 and thefirst side surface CS1 and between the first incident surface IS1 andthe third side surface CS3, respectively. In addition, auxiliarysurfaces CS2-10 and CS3-20 are disposed between the second incidentsurface IS2 and the second side surface CS2 and between the secondincident surface IS2 and the third side surface CS3, respectively.

Referring to FIG. 14F, a first light incident area AA and a second lightincident area BB of a light guide unit LG86 may be concaved from thelight exit surface US when viewed in a plan view. Auxiliary surfacesCS1-10 and CS3-10 are disposed between the first incident surface IS1and the first side surface CS1 and between the first incident surfaceIS1 and the third side surface CS3, respectively. In addition, auxiliarysurfaces CS2-10 and CS3-20 are disposed between the second incidentsurface IS2 and the second side surface CS2 and between the secondincident surface IS2 and the third side surface CS3, respectively.

FIG. 15 is an exploded perspective view showing a display deviceaccording to an exemplary embodiment of the present disclosure.

Referring to FIG. 15, the display device includes an upper protectivemember 110, a lower protective member 120, a display panel 130, asupport member 140, and a backlight unit BLU.

The upper protective member 110 and the lower protective member 120 forman outer surface of the display device. The upper protective member 110and the lower protective member 120 are coupled to each other toaccommodate other elements of the display device therein.

The upper protective member 110 is disposed on the display panel 130.The upper protective member 110 is provided with an opening portion110-OP formed therethrough to expose a portion of the display panel 130.The upper protective member 110 covers the non-display area of thedisplay panel 130.

The lower protective member 120 is disposed under the backlight unitBLU. The lower protective member 120 includes a bottom portion 122 and asidewall portion 124 bent upward from the bottom portion 122. Thebacklight unit BLU is accommodated in a space defined by the bottomportion 122 and the sidewall portion 124.

The display panel 130 displays an image. The display panel 130 is atransmissive or transflective type display panel. For instance, thedisplay panel 130 is a liquid crystal display panel or anelectrophoretic display panel. In the present exemplary embodiment, theliquid crystal display panel that includes a first substrate 132 and asecond substrate 134 will be described as the display panel 130.

The first substrate 132 includes a plurality of pixel electrodes (notshown) and a plurality of thin film transistors (not shown) each beingelectrically connected to a corresponding pixel electrode of the pixelelectrodes. The second substrate 134 includes a common electrode (notshown). A liquid crystal layer is disposed between the first substrate132 and the second substrate 134. When an electric field generatedbetween the common electrode and the pixel electrodes is controlled, thelight from the backlight unit is switched, and different images fromeach other are generated in accordance with the switching of the pixelelectrodes.

A driving chip 136 is mounted on a side portion of the second substrate134 to apply a driving signal to the display panel 130. The driving chip136 includes a data driver and a gate driver.

The support member 140 has a rectangular frame shape to overlap with thenon-display area of the display panel 130. The support member 140 isprovided with an opening portion formed therethrough. The support member140 is disposed under the display panel 130 and supports the displaypanel 130.

The backlight unit BLU includes a first light source LE1, a second lightsource LE2, which emit the light, and a light guide unit LG that guidesthe light to the display panel 130. The backlight unit BLU may includethe light guide unit shown in FIGS. 1 to 14F.

The display device further includes an optical sheet 150 and areflection sheet 160 in order to improve the efficiency of the lightprovided to the display panel 130.

The optical sheet 150 is disposed between the light guide unit LG andthe display panel 130. The optical sheet 150 includes a prism sheet 154and a protection sheet 152, which are sequentially stacked on the lightguide unit LG.

The prism sheet 154 condenses the light exiting from the light exitsurface US of the light guide unit US and passing therethrough in adirection vertical to the surface of the display panel 130. The lightpassing through the prism sheet 154 are vertically incident into thedisplay panel 130. The protection sheet 152 is disposed on the prismsheet 154 to protect the prism sheet 154 from external impacts.

Meanwhile, although not shown in figures, the optical sheet 150 furtherincludes a diffusion sheet to diffuse the light exiting from the lightexit surface US of the light guide unit LG. As an example, the diffusionsheet may be disposed between the light guide unit LG and the prismsheet 154.

The reflection sheet 160 is disposed under the light guide unit LG. Thereflection sheet 160 reflects the light leaked through the oppositesurface LS of the light guide unit LG such that the leaked light isincident into the light guide unit LG again.

Although the exemplary embodiments of the present invention have beendescribed, it is understood that the present invention should not belimited to these exemplary embodiments but various changes andmodifications can be made by one ordinary skilled in the art within thespirit and scope of the present invention as hereinafter claimed.

What is claimed is:
 1. A backlight unit comprising: a light sourceemitting light; and a light guide unit that includes a first surface, asecond surface facing the first surface, and a plurality of connectingsurfaces connecting the first surface and the second surface, the lightguide unit guide the light from the light source to the display panel,the connecting surfaces comprising: a first side surface extending in afirst direction; a second side surface facing the first side surface; athird side surface extending in a second direction substantiallyperpendicular to the first direction; and a first incident surfacedisposed between the first side surface and the third side surface, thefirst incident surface receiving the light from the light source andincluding at least one first serration pattern having a first diffusionsurface and a second diffusion surface which is closer to the third sidesurface than the first diffusion surface, wherein a first included angleof the first incident surface and the first diffusion surface is equalto or greater than about 90 degree.
 2. The backlight unit of claim 1,wherein the first included angle is equal to or smaller than 120 degree.3. The backlight unit of claim 2, wherein the first included angle ofthe first incident surface and the first diffusion surface is equal toor smaller than 117 degree.
 4. The backlight unit of claim 3, whereinthe at least one first serration pattern is provided in a plural number,wherein a second included angle of the first incident surface and thesecond diffusion surface of one of the first serration patterns isdiffer from a second included angle of the first incident surface andthe second diffusion surface of other one of the first serrationpatterns.
 5. The backlight unit of claim 4, wherein each of the firstserration patterns further comprises a third diffusion surface disposedbetween the first diffusion surface and the second diffusion surface,the third diffusion surface is substantially parallel to the firstincident surface.
 6. The backlight unit of claim 5, wherein the firstserration patterns are spaced apart from each other.
 7. The backlightunit of claim 6, wherein the second included angle surface is equal toor greater than about 35 degree and equal to or smaller than 60 degree.8. The backlight unit of claim 4, wherein the first serration patternsare spaced apart from each other.
 9. The backlight unit of claim 8,wherein the second included angle surface is equal to or greater thanabout 35 degree and equal to or smaller than 60 degree.
 10. Thebacklight unit of claim 3, further comprising: a third diffusion surfacedisposed between the first diffusion surface and the second diffusionsurface, the third diffusion surface is substantially parallel to thefirst incident surface.
 11. The backlight unit of claim 10, wherein thefirst serration pattern is provided in a plural number, wherein thefirst serration patterns are spaced apart from each other.
 12. Thebacklight unit of claim 3, wherein the first serration pattern isprovided in a plural number, wherein the first serration patterns arespaced apart from each other.
 13. The backlight unit of claim 2, whereinthe first serration pattern is provided in a plural number, wherein asecond included angle of the first incident surface and the seconddiffusion surface of one of the first serration patterns is differ froma second included angle of the first incident surface and the seconddiffusion surface of other one of the first serration patterns.
 14. Thebacklight unit of claim 13, wherein each of the first serration patternsfurther comprises a third diffusion surface disposed between the firstdiffusion surface and the second diffusion surface, the third diffusionsurface is substantially parallel to the first incident surface.
 15. Thebacklight unit of claim 14, wherein the first serration patterns arespaced apart from each other.
 16. The backlight unit of claim 15,wherein the second included angle surface is equal to or greater thanabout 35 degree and equal to or smaller than 60 degree.
 17. Thebacklight unit of claim 13, wherein the first serration patterns arespaced apart from each other.
 18. The backlight unit of claim 17,wherein the second included angle surface is equal to or greater thanabout 35 degree and equal to or smaller than 60 degree.
 19. Thebacklight unit of claim 2, wherein the at least one first serrationpattern further comprises a third diffusion surface disposed between thefirst diffusion surface and the second diffusion surface, the thirddiffusion surface is substantially parallel to the first incidentsurface.
 20. The backlight unit of claim 19, wherein the at least onefirst serration pattern includes two serration patterns, the at leastone first serration pattern further includes a portion of the firstincident surface disposed between two first serration patterns.
 21. Abacklight unit comprising: a light source emitting a light; and a lightguide unit that includes a first surface, a second surface facing thefirst surface, and a plurality of connecting surfaces connecting thefirst surface and the second surface to guide the light from the lightsource, the connecting surfaces comprising: a first side surfaceextending in a first direction; a second side surface facing the firstside surface; a third side surface that extends in a second directioncrossing the first direction; and a first incident surface disposedbetween the first side surface and the third side surface, receiving thelight from the light source, and including at least one first serrationpattern having a first diffusion surface and a second diffusion surface,wherein the first incident surface defines a first included angle withrespect to an extension surface of the third side surface, and wherein asecond included angle of the first diffusion surface with respect to thefirst incident surface is in a range determined by the followingEquation, and a third included angle of the second diffusion surfacewith respect to the first incident surface is smaller than the secondincluded angle, Equation 90≦θ2≦90+θ1, where θ2 denotes the secondincluded angle and θ1 denotes the first included angle.
 22. Thebacklight unit of claim 21, wherein the first included angle is greaterthan about 20 degrees and smaller than about 30 degrees.
 23. Thebacklight unit of claim 21, further comprising a second incident surfacedisposed between the second side surface and the third side surface,receiving the light from the light source, and including at least onesecond serration pattern.
 24. The backlight unit of claim 23, whereinthe first incident surface has a shape symmetrical with a shape of thesecond incident surface when viewed in a plan view.
 25. The backlightunit of claim 21, wherein the first serration pattern further comprisesa third diffusion surface disposed between the first diffusion surfaceand the second diffusion surface.
 26. The backlight unit of claim 21,wherein the first serration pattern is provided in a plural number. 27.The backlight unit of claim 26, wherein any one of the first serrationpatterns has a shape different from a shape of another one of the firstserration patterns when viewed in a plan view.
 28. The backlight unit ofclaim 27, wherein an included angle between the third side surface andthe second diffusion surface of each of the any one of the firstserration patterns and the another one of the first serration patternsis equal to or greater than about 35 degrees and equal to or smallerthan about 60 degrees.